Acwing 94. recursive implementation of permutation enumeration

#include<iostream>
#include<vector>
using namespace std;
int n;  
vector<int> path;
// For each number, there are two schemes: select and deselect , If elected , Data in path,state Set up 1, Finally, reply to the scene .
// Enumerate until all numbers are enumerated .

//u Indicates how many numbers are currently selected ,state Status of each number 
void dfs(int u,int state){
    if(u == n){ 
        for(auto x:path) cout << x << ' ';
        cout << endl;
        return;
    }
    
    for(int i = 0;i < n;i++){
        if(!(state >> i & 1)){
            path.push_back(i + 1);
            dfs(u + 1,state | 1 << i);
            path.pop_back();
        }
    }
}

int main()
{
    cin >> n;
    dfs(0,0);
    return 0;
}